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SEAS CNO-4
Copyright 2021 © Troels Gravesen

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DRIVERS   CROSSOVER    CABINET    MEASUREMENTS    SPEAKER-KIT     CROSSOVER LAYOUT   PASSIVE XOVER FOR BASS

CNO-4 is featuring a new 6" driver from SEAS, W18NX003, an up-date of my beloved Nextel coated driver, but here refined with new and improved magnet systems and titanium voice coil formers. The center pole piece has a conical boring focusing the magnetic field and reducing stray field. Center pole piece is copper clad in its entire length, thus better SD producing flatter impedance profile. The titanium voice coil former enhance power handling and ensures better cooling of the W18 voice coil, thus reduced distortion at high levels, i.e. better dynamic headroom.

The 8" W22NY001  features the same cone material as its 6" sibling and I've use it before. It's an easy driver and we can get away with a very simple 1st order crossover where the W18 and W22 works in a 2½-way fashion with very little phase difference.

For bass there was no doubt. The BMS 12N630. I've used this bass driver before in many constructions and it gives incredible value for money. When I first set up the CNO-4 test cabinets, I was using a vintage SEAS bass driver, the 33 F-WK-A, a magnificent 13" bass driver, but long extinct. SEAS doesn't have anything in this range at present, so BMS it must be.

T29CF002 tweeter. Can't add much to what I've said before about this dome. One of the best dome tweeters, in particular with a Amber-Z capacitor in front, but Alumen-Z takes you 99% there.

I want to reiterate that the W22+W18 runs in a 2½-way fashion - with no high-pass filter. This means the W18 gets the full signal from the deepest bass up to it's point of crossover. Not having a high-pass filter to the upper section has its indisputable benefits in terms of improved sonics - and also saving a considerable amount of money on high-quality capacitors.  It adds some extra strain on the W18 driver in particular, but with the new titanium voice coil former, it can handle a lot of power.
There's an option to further improve power handling by adding a high-pass filter before your power amplifier running the upper section, please read here: http://www.troelsgravesen.dk/High-Pass-Filter.htm
Adding a 1st order high-pass filter at ~80 Hz reduce the power input at 40 Hz by 6 dB! This makes a difference in power handling, but for most applications it may not be necessary.
Having two drivers sharing the upper-bass and midrange means quite some membrane area, so they never work too hard and even without the high-pass filter I can play louder than any visitor like without distortion from the W18 driver. This titanium voice coil formers does well!

Being very similar to my Ellipticor-3 speakers, my expectations were under control for the first listening tests. Little had I expected the level of transparency, crispness and dynamics I heard. Even the bass from the twin-drivers were surprisingly vibrant, deep and solid. This could be a candidate for a standard floor-stander 2½-way if the upper panel tilt and chamfering is kept intact. But please do not ask. Not just a matter of leaving out the BMS.

Since I received the new W18NX003 drivers they'd been sitting in my CNO-25 speakers, so they were well broken in when I moved two of them to the CNO-4 cabs. I loved what they did in CNO-25, but it wasn't until the CNO-4 set-up that I could fully appreciate the qualities of this new driver. Installing the speakers in our living room I initially didn't think them as efficient as I had expected - only to find out I was playing them louder than normal! A very good sign of low distortion. The W18NX... has all the qualities I could ask for from a 6" driver. Utterly transparent and dynamic combined with an overall smooth response that doesn't make it selective on recordings, nor favour any musical genre.
Treble? I've had the question on some of my 1st order tweeter set-ups. Where's the tweeter? Is there really enough treble level because I can't "hear" the tweeter. No, we can't hear the tweeter, we only hear treble without phase distortion and the overall tuning as fairly linear. It can take some mental adjustment, because "1st order treble" sounds quite different to treble passed through any higher order crossover. Again, the T29 is a magnificent tweeter and does very well with 1st order filters.
With the BMS 12N630 driver in place and run by the powerful 500 watts Hypex 501 we have a full-blown full-range speaker delivering a solid foundation for all kinds of music.
There will be a fully passive options as I know some people will want this, but only for bi-amping. My recommendation is the Hypex FA501 to explore the CNO-4 to its full potential.

So, to summarise, what you need to do to get the very best from this speaker is placing a small capacitor in front of your power amplifier, take the signal from the speaker wire and use the appropriate software for the FA501 - and you're flying. The FA501 program will compensate for the 1st order roll-off and thereafter provide the low-pass filter for the bass driver. Here's an illustration of what is happening.
I think I can guarantee an extraordinary performance.

 


Basics:
4-driver speaker.
Dimensions: 39 x 53x 110 cm, WxDxH.
System sensitivity: 91.5 dB/2.8V/1 meter.
Impedance: 4-8 Ohms for MMT section.
Point of crossover: 80 and 2600 Hz.
Power requirement: 20+ watts/channel.
Power handling: 100 watts. Please also read: http://www.troelsgravesen.dk/power-handling.htm, and remember any burned driver is a misused driver.

Useful links:
Please read these files before e-mailing:
http://www.troelsgravesen.dk/tips.htm
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/LCR-RC.htm

FAQ:
You cannot change cabinet front panel dimensions and drivers' placement without needing a new crossover - and I cannot help.
You cannot use any other drivers with the crossover shown here.
Please read these files before e-mailing:
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/choices.htm


 

DRIVERS
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T29CF002, 6 Ohms


W18NX003, 8 Ohms
Click images to view large


Conical boring of center pole piece, full length copper cladding, titanium voice coil former, bigger magnet.

 


W22NY001, 8 Ohms


BMS 12N630, 8 Ohms
Click images to view large

Download driver specs:  T29CF002   W18NX003  W22NY001   BMS 12N630 (8 Ohms)


CROSSOVER
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The W18NX003 LCR filter was a late addition as I wanted the W18NX003 to have as smooth a 1st order roll-off as possible, initially done quite well with an RC circuit across L2, but an LCR circuit proved just better technically - and also a little better sonically.
The tweeter circuit may look 2nd order but the value of R2 is very high and R2+L1 only helps shaping the 1st order roll-off. Several type of coils were tested for the W18 and W22 and eventually I found the foil CrossCoils performing very well, so this it will be. C1 can be Alumen-Z or Amber-Z, the latter seriously expensive. I suggest starting with the Silver-Z and should you like what you hear, you may later substitute with Alumen-Z or Amber-Z.


CABINET
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Tweeter is recessed 10 mm and I added a 10 mm panel to the 25 mm basic front panel. Cut 15 deg. towards the tweeter like seen on drawing.

Cabinets were made from 27 mm Baltic birch. You can use 20-22 mm and add 4 mm bitumen pads without changing any dimensions. The bottom dimensions, width and depth, is the actual dimension based on calculation derived from the actual tilt of sides and front. Make 390 mm width and 495 mm depth and you're fine. The added front panel for W18 and W22 is 10 mm to acoustically align the midbass and tweeter.

Cabinet damping:
Add 8 mm felt sheets to all internal panels except front panel for upper section.
Add 150 grams sheep's wool to 18W cabinet.
Cut two pieces of 30 x 50 cm acoustilux, roll it and stuff the cavity behind the 18W driver.
Cut one piece of 30 x 50 cm, fold and place on top of the crossover on W22 floor and up the sides. See image below.
Bass cabinet: Cut two pieces of 40 x 50 cm acoustilux and place over the port and down the sides.

Port for W22 cabinet: Ø68 x 220. Roll a piece of 15 x 50 cm acoustilux and stuff the port with this roll. This makes an aperiodic tuning. What is this? Read here: http://www.troelsgravesen.dk/Variovent.htm


Hypex FA251 or FA501 plate-amp/DSP

 

You can use either Hypex FA251 (250 watts/4 OHms) or FA501 (500 watt/4 Ohms) for the CNO-4. I don't recommend either of them, but use FA501 myself knowing 250 watts is more than enough. Take your pick.

Go to Hypex page to learn more:  http://www.troelsgravesen.dk/FUSION_FA251_FA501.htm
Here you also find the software for your FA501 module.


The two files.


When opening the Hypex software, HFD.
Set all presets to AnalogueSUB input and volume to 0,0 dB

Press Device settings, and you get this:


You can use the setting above, or adjust to personal preferences.

 


The program when using a high-pass filter for your power amp. 



The advantage of using the FA251 or FA501 is that you take the signal from the speaker cables and do not need a line level source from your preamplifier in case you do not have such.
The Hypex module contains a DSP, digital signal processing, where the low-pass crossover for the bass driver is implemented saving crossover components and ensuring zero resistance between power amp and driver.

Should you for some reason not favour the Hypex solution, there will be a passive crossover for the bass section - but only for bi-amping as the bass section combined with the BMT section will produce an impedance of 2 Ohms, something only a few power amplifiers will be happy with.

To make a passive crossover working at 80 Hz in a vented box requires linearisation of the upper impedance peak, thus R1/L2/C2. L1 requires a heavy high-value C-Coil with a very low DCR of 0.17 Ohm. It all works very well, but as said, recommended only for bi-amping.
The 25 mH is a cored coil from 1.0 mm wire and internal resistance of 1.07 Ohm. Capacitors are electrolytics. As often said before, there are no sonic attributes associated with deep bass except speed and the ability to move air. What matters is membrane area, driver efficiency - and not least power. We need to move as much air as possible - and we need to move it fast. Using polypropylene caps here is a total waste of money, although a lot of people don't believe it is.


Workshop images


Make test cuts of 42.5 deg. to see if it adds up as expected.


Routing for the Hypex module. This doesn't have to be flush mounted, but looks nice.


Port holes made.


Gluing the bas upper panel.


Preparing for the Hypex compartment (right image).


I like electronics to be ventilated, hence three 20 mm holes in lower panel of Hypex compartment.
The Hypex module has slots on face plate and it should now be properly ventilated.


Gluing W18 rear panel in place. Cabs ready for sanding and lacquer (right).


Gluing bass section front panel. Adjustable feet bolts, M10, glued with epoxy.


Set the saw blade to 40 deg. and the side slider to ~2 deg. and do the front panel chamfering.


Testing front panels for the T29 version. Front panel at stage in painting.


Cabs drying from final 4th lacquer coat. Add two 40 x 50 cm sheets of acoustilux above port.

 
Combine red and blue wires for PLUS and grey and black for MINUS. Bass section finished.

 


Workshop set-up. The phase plug will change color in the final samples and the W22NX001 will be replaced by black phase plugs.


The Hypex connection. As simple as that.


MEASUREMENTS
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A few comments on MEASUREMENTS before you start interpreting the readings below.
First of all, if we think measurements will tell us how a speaker sounds, we're wrong. The perception of sound is way too subjective to be reflected in any measurements we can perform. A loudspeaker system is meant to give us a satisfying idea of an acoustic event and for some people a pair of 5 USD ear-plugs are enough, others spend 200 kUSD on a truly full-range pair of speakers - and the latter may not be happier than the former.
Measurements may give us an idea of tonal balance of a system, i.e. too much or too little energy in certain areas, although dispersion characteristics play a vital role here. A two-way 7+1 and a three-way 7+4+1 may display similar horizontal dispersion, yet sound very different. Measurements may tell us about bass extension if far-field measurements are merged with near-field measurements. In addition to this, ports may contribute to bass extension. Most of we diy'ers do not have access to an anechoic room for full-range measurements from 20-20000 Hz.  
What cannot be seen is what kind of bass performance we get in a given room. Bass performance is highly dependent on in-room placement of your speaker and the same speaker can be boomy in one place and lean in another. Actual SPL level at 1 meter distance and 2.8V input is useful for en estimate of system sensitivity and combined with the impedance profile may give an idea of how powerful an amplifier is needed to drive the speaker to adequate levels.
What measurements do not tell is the very sound of the speaker unless displaying serious linear distortion. The level of transparency, the ability to resolve micro-details, the "speed" of the bass, etc., cannot be derived from these data. Distortion measurements rarely tell much unless seriously bad, and most modern drivers display low distortion within their specified operating range. 
Many people put way too much into these graphs and my comments here are only meant as warning against over-interpretation. There are more to good sound than what can be extracted from a few graphs. Every graph needs interpretation in terms of what it means sonically and how it impacts our choice of mating drivers, cabinet and crossover design.
What measurements certainly do not tell is the sonic signature of the speaker, because speaker cones made from polypropylene, aluminum, Kevlar, paper, glass fiber, carbon fiber, magnesium, ceramics or even diamonds all have their way of adding spices to the stew. Nor do measurements tell what impact the quality of the crossover components add to the sound, from state of the art components to the cheapest of coils and caps, they all measure the same if values are correct, yet sound very different.

Measuring a 2½-way speaker with 1st order crossovers is quite a challenge due to inherent crossover lobing, something that can only be done at far distance in an anechoic chamber - and I haven't got one.
Below you find the summed response of bass and midbass drivers, tweeter and summed response of midbass and tweeter.  


Red: Summed response of W22 and W18 drivers driven from crossover.
Green: T29 response driven from crossover.
As can be seen we have some 91-92 dB sensitivity from running the W18 and W22 in parallel.


Summed response of T29 and W18 drivers driven from crossover.


Final system impedance of W22/W18/T29. Talk about an easy load!
Minimum impedance 4 Ohms. Green = electrical phase.



Above the unfiltered response of the W18NX... driver in actual cabinet.
In all of the ever so important midrange - as smooth as one can hope for.


SPEAKER-KIT
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Above the level 1 parts list. For Level 2, the Amber-Z is replaced by Alumen-Z. This is the only difference.



Add-on kit for passive crossover for bass - only for bi-amping.

All kit and component prices may be subject to change and are always to be confirmed by Jantzen Audio Denmark.

Download Complete Kit Sale Presentations:

All technical questions to troels.gravesen@hotmail.com

All questions regarding purchase of kits, please mail Jantzen Audio at contact@jantzen-audio.com


CROSSOVER-LAYOUT
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Crossover layout for W18 and W22 drivers. Place crossover behind W22 driver as close to rear panel as possible.
The width is 225 mm and should fit perfectly with the width at the base of the upper pyramid with felt damping in place.


Tweeter section layout. I suggest placing in upper W18/T29 cabinet behind tweeter to get as far away from driver magnets as possible.
Use half a solder tag strip for each section.
All three attenuation resistors shown here. Connect the input wire to preferred attenuation resistor.


Tweeter section. Click images to view large.
Place tweeter crossover in upper compartment (mid + tweeter) on rear panels towards top.
Only one attenuation resistor shown here.


W22 and W18 section.


This board now weighs some 3.55 kgs (7.8lb)!
Fasten the chunky foil coils with brass screws.

More info here on heavy coils.


Speaker wiring



Add-on kit for passive crossover for bass and bi-amping:








Passive crossover layout.





Bass wiring for passive crossover.